/*
 * @(#)MD5InputStream.java   0.3-3 06/05/2001
 *
 *  This file is part of the HTTPClient package
 *  Copyright (C) 1996-2001 Ronald Tschal�r
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307, USA
 *
 *  For questions, suggestions, bug-reports, enhancement-requests etc.
 *  I may be contacted at:
 *
 *  ronald@innovation.ch
 *
 *  The HTTPClient's home page is located at:
 *
 *  http://www.innovation.ch/java/HTTPClient/ 
 *
 */

package org.everrest.http.client;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * This class calculates a running md5 digest of the data read. When the stream
 * is closed the calculated digest is passed to a HashVerifier which is expected
 * to verify this digest and to throw an Exception if it fails.
 *
 * @author Ronald Tschal�r
 * @version 0.3-3 06/05/2001
 */
class MD5InputStream extends FilterInputStream {
    private HashVerifier verifier;

    private MessageDigest md5;

    private long rcvd = 0;

    private boolean closed = false;

    /**
     * @param is
     *         the input stream over which the md5 hash is to be calculated
     * @param verifier
     *         the HashVerifier to invoke when the stream is closed
     */
    public MD5InputStream(InputStream is, HashVerifier verifier) {
        super(is);
        this.verifier = verifier;
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException nsae) {
            throw new Error(nsae.toString());
        }
    }

    public synchronized int read() throws IOException {
        int b = in.read();
        if (b != -1)
            md5.update((byte)b);
        else
            real_close();

        rcvd++;
        return b;
    }

    public synchronized int read(byte[] buf, int off, int len) throws IOException {
        int num = in.read(buf, off, len);
        if (num > 0)
            md5.update(buf, off, num);
        else
            real_close();

        rcvd += num;
        return num;
    }

    public synchronized long skip(long num) throws IOException {
        byte[] tmp = new byte[(int)num];
        int got = read(tmp, 0, (int)num);

        if (got > 0)
            return (long)got;
        else
            return 0L;
    }

    /**
     * Close the stream and check the digest. If the stream has not been fully
     * read then the rest of the data will first be read (and discarded) to
     * complete the digest calculation.
     *
     * @throws IOException
     *         if the close()'ing the underlying stream throws an
     *         IOException, or if the expected digest and the calculated
     *         digest don't match.
     */
    public synchronized void close() throws IOException {
        while (skip(10000) > 0) ;
        real_close();
    }

    /**
     * Close the stream and check the digest.
     *
     * @throws IOException
     *         if the close()'ing the underlying stream throws an
     *         IOException, or if the expected digest and the calculated
     *         digest don't match.
     */
    private void real_close() throws IOException {
        if (closed)
            return;
        closed = true;

        in.close();
        verifier.verifyHash(md5.digest(), rcvd);
    }
}
